Shaping of double-barrel blanks for shotguns



June 1960 v .1. J. PIETRINI 2,941,337

SHAPING OF DOUBLE-BARREL BLANKS FOR SHOTGUNS Filed Jan. 19, 1959 2 Sheets-Sheet l b a c FIG.2 FIG. I V FIG.3

June 1960 J. J. PIETRINI 2,941,337

SHAPING OF DOUBLE-BARREL BLANKS FOR SHOTGUNS Filed Jan. 19, 1959 2 Sheets-Sheet 2 FIG. ll

United States Patent SHAPING OF DOUBLE-BARREL BLANKS FOR SHOTGUNS Jean Jourdan Pietrini, 8 Rue Dronot, Paris, France Filed Jan. 19, 1959, Ser. No. 787,712

Claims priority, application France Jan. 21, 1958 3 Claims. (Cl. 51-33) This invention relates to the external shaping, by grinding, of blanks of metal to be formed into the doublebarrel portion of shotguns.

For the foregoing purpose, there is provided the machine described hereinafter with reference to the accompanying drawings, wherein:

Fig. 1 shows in side elevation a forged, rolled or swaged blank for the barrel.

Fig. 2 is a transverse vertical section of the blank near the stock end.

Fig. 3 is a transverse vertical section of the blank near the muzzle end.

Fig. 4 is a transverse vertical section of a grinding machine in which the blank is secured for its external shaping.

Fig. 5 is a horizontal section through part of the machine to show a detail of parallel bearing means for two grinding wheel holders.

Fig. 6 is a diagram to illustrate the manner in which the grinding wheels are brought up to the work-piece or blank at the commencement of the shaping operation.

. Fig. 7 is a diagram to show another method of shaping in which two pairs of grinding wheels are used instead of two single wheels.

Fig. 8 is a section, taken in a plane at right angles to that of Fig. 4, of the machine and showing one grinding wheel on its frame.

Fig. 9 is a partial end elevation of the machine to show drive means for the grinding wheel frame.

Fig. 10 shows a detail of adjustment means for the eccentricity of an eccentric included in the frame drive means.

Fig. 11 is an elevation of means coupling two eccen trics adjustably together.

The steel ingot from which the barrel is to be formed will, first of all, be forged, rolled or swaged into the shape shown on Fig. 1, in which a represents the body of the tubes, 1) represents the part (head) in which will be cut the pawls, a the dovetail which is to be fitted into the upper part of the stock and form the tenon which is known under the name of triple or quadruple bolt.

Irrespective of the method of making the ingot, it will receive its final shape by means of a final swaging which is mainly intended to remove any buckle which it might have undergone during the course of manufacture.

The ingot, cut to measure and trued at both ends, is bored and chambered by ordinary processes. It is then mounted upon the machine which gives it the final shape. It is then possible for the barrel to be conveyed to the final manufacturing phases, that is to say, polishing and bronzing. Countersinking for the pawls is carried out, as required according to different systems and makes.

The machine itself consists essentially of two plates facing each other and between which the double barrel is fixed horizontally. Around the axis of each tube there oscillates a set of grinding wheels which describe an arc formed by the shape of the tube at the tangential point ice 2. of the wheel with the latter. The radius and the position of the arc described varies according to Whether one works on the muzzle end, the middle or the end of the tube.

The stroke, that is to say, the amplitude of the oscillation 1 must be adjustable as well asthe position of the are on the circumference, this position being given by the two ends of the arc described or by the position of the arrow half-- way down the stroke of the grinding wheels.

The frames which carry the wheels consist essentially of two vertical legs which are connected by means of a set of rods, the whole forming a kind of frame on which is displaced a carriage to which is suspended the electric motor which carries the wheel which is mounted directly onto the axle of the motor. The frame which carries the wheels is represented, in cross section, in Fig. 4 and in longitudinal section in Fig. 8. The foot 1 is mounted upon the axis d in the manner of the small end of a connectingv rod. The set of rods g consists essentially of two or several lateral rods, and a central rod forming an endless screw driven by the oscillating movement of the frame which carries the wheels. The carriage, which carries the motor h with its wheel m, is therefore supported and guided by the lateral rods and driven by the central screw which makes it traverse the entire length of the frame, parallel to the generators of the tube.

Each frame oscillates around its tube. As the axes of the tubes are too close together for them to be used side by side, the solution adopted is the following: the

concentric to i; the whole is fixed by a strong axle to the plate j. The opposite plate supports also the bearings and the pins which are identical for the other leg of the frame which carries the wheels and for the other end of the barrel.

This device allows of having axes of considerable diameter but, to allow of full liberty of movement of the frames which carry the wheels, it is necessary for the hearings to have a greater radius than the radius of the:

frames meeting during their course, their oscillating move ment is carried out in the same direction, that is to say that the frames fg do not go towards each other,"

but follow each other, the wheels being at the end of the stroke one at the beginning, and the other at the end of the axis described and, at each moment, at symmetrical and opposite points in relation to the tangent of the are described.

This movement is carried out in the following manner: upon the bearings de, Fig. 5, are mounted with slight friction two sleeves which carry, on their rear edge, a toothed wheel. The two gears are opposite each other and separated by some millimetres; they are engaged by a loose pinion w (Fig. 4) which is situated at the intersection of the two circumferences. On the sleeves of the toothed wheels are mounted the feet 1 of the frames which carry the grinding wheels, in the manner of small ends of connecting rods, of which the tightening can be regulated.

0p87afl OIl'.-T he plate which is in front of the machine, shown in profile in Fig. 8 and frontally in Fig. 9, carries, at its base, a hollow axle upon which is mounted a toothed wheel k shown in detail in Figs. 10 and 11. This wheel is Patented June 21, 1960 amiss-1 a plate mounted upon the hollowaxis and carries, diametrically, a screw r (Fig; 10), which turns in two small bearings r r which are fixed to the plate k at the two; extremities of the diameter. This screw r carries,

in its middle, a cylindrical toothed component cr which" is'driven by' a rack cr Against the plate k is mounted a second plate k which has a large di'ametral' recess t in which is housed the screw r of plate k. Two internally threaded runner collarss, s carried on the screw r are secured'to theplate k and serve to retain it against plate k whilst permitting diametral movement with respect thereto. The two plates are thus integral, their respective positions being able to go from concentricity to maximum eccentricity allowed by the rotary motion of the screw r.

The plate k is engaged, with its external teeth, with the screw v which is mounted upon the shaft of the motor M (Fig. 9). The plate k' which is superimposed, carries an eccentrichoop with its connection-rod l which gives the handle of the pinion n which is engaged with pinion p, of which the diameter is equal to half that of n. On'Figi Sis shown the pinion p the shaft of which carries, at itsother extremity, the pinion p drives'the gear wheel of the frame which turns on bearing e. The movement is transmitted to the second gear wheel which drives the turning frame on d through the intermediary of the pinion w (Fig. 4).

The amplitude ofthe oscillation, and therefore, of the arc described by the wheels, is determined by the eccentric assembly k, k. Its eccentricity can be regulated by the rotary motion of the screw r (Fig. For this purpose, a rack or by engaging with the toothed part cr penetrates into the hollow axis of the plate k'and causes the screw rto turn, by'increasing or decreasing the eccentricity of plate-k in relation to plate k.

' The are described by the wheels atthe surface of the barrels is characterised by:

(1) Its length (2) Itsposition.

The-length of the arc is expressed bythe number'of degrees which it-takes up on the circumference. Its position can be defined by the positionof its sweep in relation to a line of reference, such as the vertical diameter. Hence the means oil-regulating the machine: the arc to be described being determined by its span and its sweep, the eccentric and consequently, the handle (or pin) o'(Fig. 9) is taken at-half-stroke. Then, by-actingupon the arms of the frames which carry the wheels, the wheels are brought onto the sweeps (Fig. 6). The machine is then started up. At each oscillation, the carriage which carries the frame-bearing wheels advances towards the end of the barrel, underthe impulse of the central screw of the frame-carrying wheel. The screw is operated as follows: at its end is fixed a pinion mounted upon a free wheelx (Fig. 8) which engages in a toothed sector which is fixed to the plate. Thus, the rotation of the lead-screw is alwaysearriedoutin thesamedirectiom To avoid. any. mechanical complications, the lead screw can be kept parallel to the axis of the tubes. It is only the guiderods which are to be arranged parallel to the tube generators, the vertical play required being provided for in the fixing of the drive screw of, the carriage.

The grinding can be carried out in two ditierent ways: the wheels can be arranged in the radial plane, that is to say, in the plane which goes through the axis of the tube (Fig. 6.),0r else tangentially, that is to say, ona plane which is tangential to the generators of the tube (Fig. 7). In this case, a second wheel can be arranged parallel to the first,.an-d the are described by the machine can be reduced by half.

The manufacture of double barrels for shotguns by this process, could comprise two phases: a first shaping would be obtained by a machine which was equipped with large capacity wheels. That would be the roughing-down stage which would'bring the barrelsto within a few tenths of a millimetre of the final figure. The barrels would then be mounted upon a machine with very fine grinding wheels, where theywould be finished and polished as. in the case of a piece which was submitted for truing.

l. A machine for grinding a metal blank in thepro-v duction of the barrel portion of double-barreled sporting guns, comprising a machine frame, means for rigidly securing the blank: in position in said frame, first bearing means mounted on the frame and coaxial with a first barrel of the. gun, second bearing means mounted on the frame coaxial with a second other barrel of the gun, a first guide structure rotatably mounted on the first bearing means and including guide means, parallel to the intended ground tapered external surface of the first barrel, a second guide structure rotatably mounted on the second'bearing means and including guide means parallel to the intended ground tapered external surface of the secondbarrel, twocarriages mounted on and movable one along each guide means, grinding wheelmeans on each carriage, and mean for reciprocating the guide structures in synchronism about their bearing axes.

2. A grinding machine, as claimed in claim 1, including means for shifting the carriages a predetermined distance along their respective guide means at each move ment of reciprocation of the guide structures.

3. A grinding machine, as claimed in claim 1, wherein the. reciprocating means include an eccentric the throw ofwhich is adjustable for adjustment of the length of arc through which the guide structures move.

References Cited in the file of this patent UNITED STATES PATENTS 

